In a macromolecular/liquid crystal composite film with smectic liquid crystals dispersed and fixed in UV-setting type resin, it is known that smectic liquid crystals are in a non-oriented state when prepared and are opaque because of scattering caused by the difference of refractive indices between the liquid crystals and resin, and that, when voltage is applied, the liquid crystals are oriented in the direction of the electric field, scattering is eliminated and liquid crystals are turned to transparent because the refractive index concurs with that of the polymer. The composite film has a memory property, and even when voltage is applied once to orient the liquid crystals and the electric field is removed thereafter, the oriented state is maintained. This oriented state can be turned again to a non-oriented state when the medium is heated to change the liquid crystal layer to a isotropic phase and is cooled down to room temperature. When the composite film is formed on glass where a transparent electrode such as ITO is deposited and a photoconductive layer formed on glass where the ITO electrode is deposited and these are placed face-to-face with an air gap between them, and when image exposure is performed from the direction of the photoconductive layer side and voltage is applied between the two electrodes at the same time, high resolution image recording can be performed in an analog manner. In this case, on the portion exposed to light, resistance of the photoconductive layer decreases, and electric current increases compared with that of the dark portion. Voltage is applied more on the liquid crystal medium opposed to it than on the dark portion. Thus, liquid crystals are oriented and turned to transparent, and an image can be recorded.
FIG. 1 shows an arrangement of an image recording apparatus using a polymer dispersion liquid crystal medium as described above. In the figure, reference numeral 10 represents a photosensitive member, and 20 a liquid crystal recording medium. The photosensitive member 10 comprises a transparent electrode 12 and a photoconductive layer 13 sequentially laminated on a transparent support member 11, and the liquid crystal recording medium 20 comprises an electrode 22 and a polymer dispersion liquid crystal layer 23 sequentially laminated on a support member 21. As the photoconductive layer, a single photoconductive layer added with amorphous selenium, amorphous silicon, etc. as an inorganic conductive layer or added with trinitro-fluorenone to polyvinyl carbazole as an organic photoconductive layer may be used. Alternatively, a photoconductive layer may be used, which comprises an electric charge generating layer where an azo pigment dispersed on a resin such as polyvinyl butyral and an electric charge migration layer where a hydrazone derivative is mixed with a resin such as polycarbonate and both layers are laminated each other. As the electrode 22 of the liquid crystal recording medium, a transparent electrode such as ITO or non-transparent electrode such as aluminum electrode may be used. (FIGS. 1-7 represent prior art.)
When the photosensitive member 10 and the liquid crystal recording medium 20 are placed face-to-face and voltage is applied between the two electrodes 12 and 22 from a power source 30, and visible light is irradiated as a writing light, the electrical conductivity of the photo-conductive layer 13 changes according to the intensity of light exposure, and voltage applied on the liquid crystal layer 23 changes. As a result, the oriented state of the liquid crystal layer is changed, and this state is maintained even after the applied voltage is turned off and the electric field is removed, and image information is thus recorded.
Information can also be recorded as follows: As shown in FIG. 2(a), the liquid crystal recording medium is oriented by applying voltage over the entire surface of the medium using a corona charger 32 to turn the entire surface to transparent. Then, as shown in FIG. 2(b), the liquid crystal layer is partially heated using a thermal head 33 to turn it to a non-oriented state.
The information thus recorded can be converted to an electric signal by a reader shown in FIG. 3. Specifically, of the light of a light source 4, only the light beam having an adequate wavelength is irradiated on a liquid crystal recording medium 20 through a filter 5 and it is modulated on the liquid crystal recording medium because transmittance differs according to the recorded information. The modulated light is received by a photoelectric converter 6 such as a CCD line sensor and is converted to an electric signal. This electric signal can be outputted by a CRT or printer when necessary.
As shown in FIG. 4 and FIG. 5, an information recording medium is also proposed, in which a photosensitive member and a liquid crystal recording member are laminated and integrated.
FIG. 4 shows an information recording medium, in which a photosensitive member 10 comprising a transparent electrode 12 and a photoconductive layer 13 laminated onto transparent support member 11 and a liquid crystal recording medium 20 having a polymer dispersion liquid crystal layer 23 laminated on a transparent electrode layer 22 are integrated. FIG. 5 shows an information recording medium, in which a photosensitive member 10 and a liquid crystal recording medium 20 are integrated via a dielectric intermediate layer 16. In case of the integrated information recording medium, there is no need to have the dielectric intermediate layer if the photoconductive layer is made of inorganic material, but the intermediate layer may be required if an organic photoconductive layer is used. In this case, an inorganic oxide film such as SiO.sub.2 or a layer coated with fluororesin such as Saitop (Asahi Glass Co., Ltd.), or polyparaxylylene may be used.
To record information on the integrated information recording medium, voltage is applied between the transparent electrode layers 12 and 22 from the power source 30, and visible writing light is irradiated on the information recording medium. Then, the conductivity of the photoconductive layer 13 changes according to light intensity, and the electric field applied on the liquid crystal layer 23 changes. As a result, the oriented state of the liquid crystal medium changes according to the intensity of the writing light, and the state is maintained even after the electric field is turned off. To read the information thus recorded, reading light is irradiated on the information recording medium from a light source 4. As the light source 4, a white light source such as a xenon lamp, halogen lamp, etc. or laser beam may be used. The incident light is modulated on the information recording medium and is converted to an electric signal by a photoelectric converter 6 such as a photodiode, CCD line sensor, etc.
In the polymer dispersion liquid crystal layer, the difference between transmittance in a oriented state and transmittance in a non-oriented state is small. When white light is used as a writing light, contrast is low, and the read image is not satisfactory. Namely, the polymer dispersion liquid crystal layer has a spectral property as shown in FIG. 8. In FIG. 8, T1 represents transmittance of a liquid crystal layer in a non-oriented state, and T2 shows transmittance of a liquid crystal layer in an oriented state. As it is evident from the property T1, transmittance to light between visible light and infrared light is high even in an non-oriented state. Because the contrast ratio (ratio of T1 to T2) with an oriented state is small, a satisfactory image cannot be obtained, and only the electric signal with a lower S/N ratio can be obtained. For this reason, when the image is read using white light as the reading light, visible light and infrared light pass through even the unreacted portion, and satisfactory contrast cannot be obtained.
In a conventional type photosensitive member, absorption in the ultraviolet and blue range is high, and the light of the ultraviolet or blue range does not pass through the photosensitive layer in the case of an information recording medium, which comprises a photosensitive member and liquid crystal recording layer laminated to each other. Thus, the image cannot be read.
When one tries to read the recorded image at high resolution, noise similar to the granularity noise of silver salt negative film is measured depending upon the condition of phase separation of the liquid crystal layer and polymer, and only the image totally coarse and rough can be obtained.